Filtered air moving apparatus

ABSTRACT

A filtered air moving device including a housing defining an air inlet, an air outlet, and an air flow path therebetween; a blower disposed in the housing and arranged to move air in the flow path from the inlet to the outlet; a multiple speed electrical motor rotatably coupled to the blower; and an air filter disposed within the housing in the air flow path. Also included is a control circuit for connecting the motor to a voltage source and including an electrical switch operable between a first condition providing rotation of the blower at a given speed and a second condition providing rotation of the blower at a predetermined speed greater than the given speed; a tubulation providing communication between a location in the air flow path downstream of the filter and a position remote therefrom; an indicator responsive to the rate of air flow through the tubulation; and a selector for varying the level of resistance to air flow provided by the tubulation.

BACKGROUND OF THE INVENTION

This invention relates generally to an air cleaning device and, moreparticularly, to a portable air cleaning device that utilizes areplaceable filter cartridge for removing undesirable particulates froma moving stream of air.

Many air cleaning devices employ replaceable filters formed of anabsorbent material that is arranged to establish a circuitous path forair flow produced by an electrically powered blower. During normaloperation of such air cleaning devices, the filters progressivelyaccumulate particles that reduce the filters permeability. Eventually,the air flow through the cleaning device becomes diminished by filterclogging to significantly reduce air cleaning efficiency. At that time,a filter must be replaced to restore efficient cleaning operation.

To assist a user in maintaining efficient cleaning operation, some aircleaning devices are equipped with indicators for monitoring thecondition of a filter and indicating when it should be replaced. Onesuch indicator consists of a transparent, vertically disposed tubehaving a lower end at atmospheric pressure and an upper endcommunicating with an internal portion of the cleaner downstream fromthe filter. As the filter becomes clogged with particulate matter toreduce air flow, an increased pressure drop occurs across the filter anda negative pressure is produced downstream thereof. The resultantdifferential pressure across the indicator tube creates an increased airflow that lifts a float member to provide an indication of adysfunctional filter. Air cleaning devices employing filter replacementfloat indicators are disclosed, for example, in U.S. Pat. Nos. 3,071,914and 5,131,932. A problem associated with float type indicators is thatair flow through the indicator tube is dependent upon the magnitude ofnegative pressure created by the electrically operated blower. Thus, inair cleaning devices employing blowers with multiple speed motors, someform of indicator calibration is required for different blower operatingspeeds.

The object of this invention, therefore,is to provide an air cleaningdevice with an improved filter replacement indicator.

SUMMARY OF THE INVENTION

The invention is a filtered air moving device including a housingdefining an air inlet, an air outlet, and an air flow path therebetween;a blower disposed in the housing and arranged to move air in the flowpath from the inlet to the outlet; a multiple speed electrical motorrotatably coupled to the blower; and an air filter disposed within thehousing in the air flow path. Also included is a control circuit forconnecting the motor to a voltage source and including an electricalswitch operable between a first condition providing rotation of theblower at a given speed and a second condition providing rotation of theblower at a predetermined speed greater than the given speed; atubulation providing communication between a location in the air flowpath downstream of the filter and a position remote therefrom; anindicator responsive to the rate of air flow through the tubulation; anda selector for varying the level of resistance to air flow provided bythe tubulation. The indicator monitors the condition of the filter andvariation in the resistance to air flow compensates for the effect ofdifferent blower speeds.

According to one feature, the device includes a manually operableactuator for simultaneously controlling the selector means and thecondition of the electrical switch. The actuator automaticallycompensates rate of air flow in response to change in blower speed.

According to another feature of the invention, the actuator controls theselector to establish for the tubulation one level of resistance to airflow for the first condition of the electrical switch and another levelof resistance to air flow greater than the one level for the secondcondition of the electrical switch means. The increased blower speed inthe second switch condition is compensated by the greater air flowresistance.

According to another feature of the invention, the selector varies theminimum orifice size provided by the tubulation. Variation in minimumorifice facilitates the desired change in air flow resistance.

According to yet another feature of the invention, the tubulationincludes a transparent vertical section having an upper endcommunicating with the location and a lower end communicating with theposition, and the indicator means is a float member disposed in thetransparent vertical section. A visual indication of filter condition isefficiently provided by this simple structure.

According to a further feature of the invention, the switch is a rotaryswitch and the selector is a rotatable valve disposed in the tubulation.Desired simultaneous control of speed and air flow is simplified by theuse of rotary components.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the invention will become moreapparent upon a perusal of the following description taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of an air cleaning device according to theinvention;

FIG. 2 is a perspective view of the device shown in FIG. 1 with an inletdoor opened to provide access to an air filter cartridge;

FIG. 3 is a perspective view of an air filter cartridge used in thedevice shown in FIGS. 1 and 2;

FIG. 4 is a partially cut away perspective view of the device shown inFIGS. 1 and 2;

FIG. 5 is a side view of a control assembly utilized in the device ofFIGS. 1 and 2;

FIG. 6 is a schematic circuit diagram of a control circuit used in thedevice of FIGS. 1 and 2;

FIG. 7 is a cross-sectional view of a selector valve of the controlassembly shown in FIG. 5 and shown in a one operating position; and

FIG. 8 is a cross-sectional view similar to that shown in FIG. 7 butwith the selector valve in a different operating position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An air cleaning device 11 includes a portable housing 12 having at oneend a grill work that defines an air inlet 13 and at an opposite end agrill work that defines an air outlet 14. Disposed between the air inlet13 and the air outlet 14 is a control panel 15 that includes a powerlight 16 and a manual actuator knob 17. Also included on the controlpanel 15 is a vertically oriented transparent viewing tube 18 retaininga float member 19. An atmospheric aperture 21 is formed in the controlpanel 15 below the actuator knob 17. Extending out of the housing 12 isan electrical cord 22 having a plug 23 for insertion into a conventionalpower outlet socket (not shown).

As shown in FIG. 2, a side door 25 of the housing 12 defines the inlet13 and is hingedly attached to the housing 12 so as to be movable intoan open position. In its open position, the end wall 25 providesphysical access to a removable filter cartridge 27 retained within thehousing 12. The filter cartridge 27 is conventional and includes anouter case 28 retaining a permeable fibrous filter material 29 thataccommodates air flow while trapping particulate material entrained inthat air flow.

As shown in FIG. 4, the housing 12 and an internal curved baffle 31define an air flow path 32 extending between the air inlet 13 and theair outlet 14 and including the filter cartridge 27. Mounted in the airflow path 32 in a location 30 downstream from the filter cartridge 27 isan air moving assembly 35 consisting of a blower wheel 36 and a multiplespeed motor 37 rotatably coupled thereto. Retained within the housing 12is a tubulation 41 that includes the vertically oriented viewing tubeportion 18 shown in FIGS. 1 and 2. A lower open end 42 of the tubulation41 communicates with the atmospheric aperture 31 in the housing 12 whilean upper end 43 opens into the location 30 within the housing 12downstream from the filter cartridge 27. Mounted in the tubulation 41between the viewing tube 18 and the lower end 42 is a rotary selectorvalve 46 (FIGS. 7 and 8). As shown in FIG. 5 the selector valve 46 isrotatably coupled to the actuator knob 17 (FIGS. 1 and 2) by a shaft 47.Also rotatably coupled to the selector valve 46 by a shaft 48 is amultiple contact rotary electrical switch 49 having electrical leads51-53.

A control circuit 55 (FIG. 6) connects the rotary switch 49 between theplug 23 and windings 57 of the motor 37. The electrical switch 49includes a movable contact 61 shown by solid lines in an open positionin FIG. 6. Rotation of the switch 49 into a first operating conditionmoves the contact 61 into electrical engagement with a first contact 62while rotation of the switch 49 into a second operating condition movesthe movable contact 61 into electrical engagement with a second contact63. In the first operating condition of the switch 49, voltage at theplug 23 is applied through the closed contacts 61, 62 across only aportion 66 of the motor windings 57 to produce a first low speedoperational mode of the motor 37 and blower wheel 36. Conversely, in thesecond operating condition of the switch 49, voltage at the plug 23 isapplied through the closed contacts 61, 63 across the full winding 57 toestablish a second operational mode with a greater rotational speed forthe motor 37 and blower wheel 36.

The selector valve 46 (FIGS. 7 and 8) includes a rotatable valve body 71that is fixed for rotation with the shafts 47 and 48. Formed in thevalve body 71 are a large orifice channel 72 and a small orifice channel73 disposed perpendicular thereto. The large orifice channel 72 has adiameter equal to that of the tubulation 41 while the small orificechannel 73 has a substantially reduced diameter. In response to rotationof the actuator knob 17, the valve body 71 is rotated simultaneouslywith the rotary switch 49. With the rotary switch 49 in its firstoperating condition, the valve body 71 is disposed as shown in FIG. 7with the large orifice channel 72 aligned with the tubulation 41.Conversely, with the rotary switch 49 in its second operating condition,the valve body 71 is rotated into the position shown in FIG. 8 with thesmall orifice channel 73 aligned with the tubulation 41 and therebyincreasing therein the resistance to air flow. Thus, in the secondoperating condition of the switch 49 produced by the actuator knob 17,the minimum orifice of the tubulation 41 is substantially reduced by thesmall orifice channel 73 of the valve body 71.

OPERATION

In response to insertion of the plug 23 into a suitable ac outlet androtation of the switch 49 into one of its operating positions, the motor37 is energized into either its high or low speed condition. Resultantrotation of the blower wheel 36 sucks air into the air inlet 13 andthrough the filter cartridge 27 for centrifugal discharge through theair outlet 14. Under normal conditions, the permeability of the filtercartridge 27 produces a relatively small pressure drop across the filtercartridge 27 and creates through the tubulation 41 between its lower end42 and its upper end 43 a rate of air flow that is insufficient to liftthe float member 19 out of a first position in the viewing tube 18 shownby solid lines in FIGS. 1 and 2. However, when particle clogging hasreduced the permeability of the filter cartridge 27 to a predeterminedlimit, an increase occurs in the pressure drop across the filtercartridge 27 and a negative pressure at the internal housing location30. The resultant increased pressure differential between the inlet 42and outlet 43 of the tubulation 41 produces therein an increased rate ofair flow that lifts the float 19 into a second upper position shown bydotted lines in FIGS. 1 and 2 and indicating the desirability for filterreplacement.

With the rotary switch 49 in its first operating condition and the motor37 operating at low speed, the minimum orifice of the tubulation 41including the large orifice channel 72 of the valve body 71 will createthrough the viewing tube 18 a rate of air flow sufficient to lift thefloat member 19 only after the sensed permeability of the filtercartridge 27 has reached the predetermined minimum limit. It will benoted, however, that in the absence of the selector valve 46, operationof the motor 37 in its high speed condition would increase the negativepressure within the interior housing location 30 resulting in a higherrate of air flow through the tubulation 41. Accordingly, the float 19would rise in the viewing tube 18 even though the permeability of thefilter cartridge 27 had not been reduced to the predetermined minimumreplacement level. This undesirable circumstance is corrected byrotation of the selector valve body 71 into the position shown in FIG. 8simultaneously with rotation of the switch 49 into a position to producehigh speed operation of the motor 37. In the second operating conditionof the valve body 71 shown in FIG. 8, the small orifice channel 73introduces in the tubulation 41 a reduction in minimum orifice size thatpermits a sufficient rate of air flow to raise the float member 19 inthe viewing tube 18 only when the permeability of the filter cartridge27 has been reduced to the predetermined replacement level.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. For example, couplingarrangements other than specifically described can be used between theselector valve 46 and the switch 49. It is to be understood, therefore,that the invention can be practiced otherwise than as specificallydescribed.

What is claimed is:
 1. Filtered air moving apparatus comprising:housingmeans defining an air inlet, an air outlet, and an air flow paththerebetween; a blower means disposed in said housing means and arrangedto move air in said flow path from said inlet to said outlet; a multiplespeed drive means rotatably coupled to said blower; air filter meansdisposed within said housing means in said air flow math; control meansfor alternatively producing either a first operational mode providingrotation of said blower at a given speed or a second operational modeproviding rotation of said blower at a predetermined speed greater thansaid given speed; tubulation means providing fluid communication betweena particular location in said air flow path and a position separate fromsaid particular location; indicator means for indicating a predeterminedclogged condition of said air filter means in response to the rate ofair flow through said tubulation means; and selector means for varyingthe level of resistance to air flow provided by said tubulation means.2. An apparatus according to claim 1 including manually operableactuator means for simultaneously controlling said selector means andsaid condition of said electrical switch means.
 3. An apparatusaccording to claim 2 wherein said actuator means controls said selectormeans to establish for said tubulation means one level of resistance toair flow for said first condition of said electrical switch means and adifferent level of resistance to air flow greater than said one levelfor said second condition of said electrical switch means.
 4. Anapparatus according to claim 3 wherein said selector means varies theminimum orifice size provided by said tubulation means.
 5. An apparatusaccording to claim 4 wherein said actuator means controls said selectorto reduce said minimum orifice size in response to a change from saidfirst to said second condition of said electrical switch means.
 6. Anapparatus according to claim 5 wherein said tubulation means comprises atransparent vertical section having an upper end communicating with saidlocation and a lower end communicating with said position, and saidindicator means comprises a float member disposed in said transparentvertical section.
 7. An apparatus according to claim 6 wherein saidelectrical switch means comprises a multiple contact switch forestablishing said first and second conditions.
 8. An apparatus accordingto claim 7 wherein said switch is a rotary switch and said selectormeans comprises a rotatable valve coupled to said rotary switch anddisposed in said tubulation means.
 9. An apparatus according to claim 1wherein said selector means varies the minimum orifice size provided bysaid tubulation means.
 10. An apparatus according to claim 9 whereinsaid actuator means controls said selector to reduce said minimumorifice size in response to a change from said first to said secondcondition of said electrical switch means.
 11. An apparatus according toclaim 10 wherein said tubulation means comprises a transparent verticalsection having an upper end communicating with said location and a lowerend communicating with said position, and said indicator means comprisesa float member disposed in said transparent vertical section.
 12. Anapparatus according to claim 11 wherein said electrical switch meanscomprises a multiple contact switch for establishing said first andsecond conditions.
 13. An apparatus according to claim 12 wherein saidswitch is a rotary switch and said selector means comprises a rotatablevalve coupled to said rotary switch and disposed in said tubulationmeans.
 14. An apparatus according to claim 1 wherein said tubulationmeans comprises a transparent vertical section having an upper endcommunicating with said location and a lower end communicating with saidposition, and said indicator means comprises a float member disposed insaid transparent vertical section.
 15. An apparatus according to claim14 wherein said electrical switch means comprises a multiple contactswitch for establishing said first and second conditions.
 16. Anapparatus according to claim 15 wherein said switch is a rotary switchand said selector means comprises a rotatable valve coupled to saidrotary switch and disposed in said tubulation means.
 17. An apparatusaccording to claim 1 wherein said position is at substantiallyatmospheric pressure.
 18. An apparatus according to claim 1 wherein saidblower means is in said air flow path downstream from said filter means.19. An apparatus according to claim 1 wherein said particular locationis downstream from said filter means, said drive means is a multiplespeed motor and said control means comprises circuit means forconnecting said motor to a voltage source, and said circuit meansincludes electrical switch means operable between a first conditionproviding said first operational mode and a second position providingsaid second operational mode.
 20. An apparatus according to claim 1wherein said tubulation means comprises hollow cylindrical tubing.